Visible rays cutoff and infrared transmission properties of TeO2–GeO2–V2O5–PbF2 glass systems

Visible rays cutoff infrared transmitting glasses in TeO₂–GeO₂–V₂O₅–PbF₂ glass systems were investigated. Glasses without OH⁻ absorption band transmitting wavelength regions from 2·0 to 5·0 nm were obtained. The addition of fluoride to these glasses and the treatment of dry-air-bubbling during melting decreased markedly absorption coefficient and reflectivity of OH⁻ bands. Reflectivity of OH⁻ bands increased with increasing absorption coefficient. Values of glass transition points from 520 to 540 °C and flow points from 560 to 580 °C were obtained.     

Thermodynamic modeling and phase diagram prediction of salt lake brine systems Ⅱ. Aqueous Li~+-Na~+-K~+-SO_4~(2-) and its subsystems

It is still a challenging task to accurately and temperature-continuously express the thermodynamic properties and phase equilibrium behaviors of the salt-lake brine with multi-component,multitemperature and high concentration.The essential subsystem of sulfate type brine,aqueous Li~+-Na~+-K~'-SO_4~(2-) and its subsystems across a temperature range from 250 K to 643 K are investigated with the improved comprehensive thermodynamic model.Liquid parameters(Δg_(IJ),Δh_(IJ),and ΔC_(p,IJ)) associated with the contributions of Gibbs energy,enthalpy,and heat capacity to the binary interaction parameters,i.e.the temperature coefficients of eNRTL parameters formulated with a Gibbs Helmholtz expression,are determined via multi-objective optimization method.The solid constants Δ_fG_k°~((298.15)) and Δ_fH_k°~((298.15)) of11 solid species occurred in the quaternary system are rebuilt from multi-temperature solubilities.The modeling results show the accurate representation of(1) solution properties and binary phase diagram at temperature ranges from eutectic points to 643 K;(2) isothermal phase diagrams for Li_2SO_4-Na_2SO_4-H_2O,Li_2SO_4-K_2SO_4-H_2O and Na_2SO_4-K_2SO_4-H_2O ternary systems.The predicted results of complete structure and polythermal phase diagram of ternary systems and the isothermal phase diagrams of quaternary system excellently match with the experimental data.     

Catalytic reactivity and surface chemistry of polyaniline(EB)–Pd–H2O systems

Catalytic reactivity and surface chemical effects induced by the presence of water in the molecular system polyaniline(EB)–Pd–H₂O were investigated. The polyaniline(EB) doped with palladium reveals its high activity and selectivity in the semihydrogenation: hexyne → hexenes (→ hexane). However, to demonstrate these effects, the specimen has to be submitted to a special treatment to lose most of its water. The XPS analysis allowed identification of the catalytically active sites of the studied system. They were ascribed to the [PdCl₄]²⁻ complex anions present at the surface of the dry specimens. This revised version was published online in August 2006 with corrections to the Cover Date.     

Modified COSMO-UNIFAC model for ionic liquid–CO2 systems and molecular dynamic simulation

A new predictive molecular thermodynamic model (i.e., modified COSMO-SAC-UNIFAC) was first proposed and extended to predict the solubility of CO₂ in pure and mixed ionic liquids (ILs) at the temperatures down to 263.2 K. It is interesting to discover that with equimolar amounts, the solubility of CO₂ in such 1:1 IL pairs, that is, [A₁][B₁] + [A₂][B₂] and [A₁][B₂] + [A₂][B₁], was consistent at the same temperature and pressure in the case of exchanging their respective cations and anions. The molecular dynamic (MD) simulation for CO₂ + mixed ILs was performed to deeply analyze and explain this intriguing phenomenon. Not only the CO₂ gas drying experiment with the ILs ([C2mim][OAc], [C2mim][dca], and [C2mim][OAc] + [C2mim][dca]) as absorbents but also the corresponding process simulation and optimization were made to stress the effectiveness and applicability of the new thermodynamic model. Thus, this work ranges from molecular level to systematic scale.     

High temperature sintering of SiC with oxide additives: I. Analysis in the SiC–Al2O3 and SiC–Al2O3–Y2O3 systems

The vaporization behaviour of pure Al₂O₃, Y₂O₃ and SiC as well as SiC–Al₂O₃ and SiC–Al₂O₃/Y₂O₃ mixtures has been analysed by thermodynamic calculations in an open system. Pure Al₂O₃ and Y₂O₃ evaporate congruently in the 1200–2300 K temperature range. Pure SiC vaporizes in a non-congruent manner leading to graphite formation as by-product. A SiC–Al₂O₃ mixture evaporates congruently according to the main vaporization reaction, 2 SiC(s) + Al₂O₃(s) +Al₂O(g) ⇆ 2 SiO(g) + 2 CO(g) +4 Al(g), but the overall composition changes: for SiC rich samples, the mixture tends towards pure SiC in time, and for Al₂O₃ rich samples towards pure Al₂O₃. A SiC–Al₂O₃/Y₂O₃ mixture shows similar behaviour.     

Measurement and prediction of isothermal vapor–liquid equilibrium of a-pinene + camphene/longifolene + abietic acid + palustric acid + neoabietic acid systems

The vapor–liquid equilibrium(VLE) data of a-pinene + camphene + [abietic acid + palustric acid + neoabietic acid] and a-pinene + longifolene + [abietic acid + palustric acid + neoabietic acid] systems at 313.15 K,333.15 K and 358.15 K were measured by headspace gas chromatography(HSGC). These data was compared with the predictions value by conductor-like screening model for realistic solvation(COSMO-RS).Moreover, the calculated data of COSMO-RS and Non-Random Two-Liquids(NRTL) models showed good...     

Comparative studies on the bioactivity of some borate glasses and glass–ceramics from the two systems: Na2O–CaO–B2O3 and NaF–CaF2–B2O3

Combined FTIR spectroscopy and X-ray diffraction analysis have been employed to investigate the bone-bonding ability or bioactivity of some prepared borate glasses and their glass–ceramic derivatives from the two systems (Na₂O–CaO–B₂O₃) and (NaF–CaF₂–B₂O₃). The present study includes the mentioned FTIR spectral and X-ray analytical techniques before and after immersion of the glasses and glass–ceramics for 2 weeks in 0.025 M sodium phosphate (Na₂HPO₄) solution. Also, the work extends to evaluate the corrosion behavior for specified grains of the studied samples (0.3–0.6 mm) after immersion in phosphate solution for 2 weeks at 37 °C. The FTIR spectra of the two glass systems after immersion show some changes in the vibrational bands than before immersion. The generation of the characteristic peaks at about 580 and 680 cm⁻¹ after immersion confirms the bone bonding ability by the formation of hydroxyapatite phase. The X-ray diffraction studies show the separation of (CaF₂) which is known to be an efficient nucleator. Weight loss data show a difference in solubility in the sodium phosphate solution between fluoride and oxide glass systems due to the strong action of the leaching solution and ease of solubility of fluoride glasses than corresponding oxide glasses in this solution. SEM data indicate the formation of small rounded or nodular shape crystals which are characteristics for the formation of hydroxyapatite layer and complete agreement with X-ray data.     

Degradation-controlling mechanisms in natural organic acid solutions of CaO–Al2O3–SiO2–B2O3 glass-ceramics by partially substituting Ca2+ with Ba2+ and Sr2+

The degradation of environmentally friendly CaO–Al₂O₃–SiO₂–B₂O₃ (CASB) glass-ceramics, which consist of anorthite and glass phase, was investigated in three natural organic acid solutions. The results indicated that citric acid had the most significant effect on the degradation of CASB glass-ceramics. While the chemical stability of anorthite is relatively poor, the glass phase also contributed significantly to the effective degradation of CASB glass-ceramics. Subsequently, Ba²⁺ or Sr²⁺ was used for full or partial substitution of Ca²⁺ in CASB glass-ceramics, and the degradation-controlling mechanism of the substituted CASB glass-ceramics was further researched. The full substitution of Ca²⁺ in CASB glass-ceramics by the two cations resulted in the occurrence of borate [BO₄] units in the glass phases, and the interlinkage of [BO₄] with broken silicate [SiO₄] network structures caused a complementary network effect. Consequently, the degradation of CASB glass-ceramics by organic acids was reduced due to the improvements in the chemical stability of the modified glass-ceramics. Additionally, degradation control can also be achieved based on a mixed-alkali effect, originating from the partial substitution of Ca²⁺ in CASB glass-ceramics by Ba²⁺ or Sr²⁺. The degradable glass-ceramics have the potential to be applied in low-temperature co-fired ceramic technology because of their good physical properties, which include a dielectric constant of 3–5, a dielectric loss as low as 10⁻³, a coefficient of thermal expansion of 3–9 × 10⁻⁶/°C, and an average bending strength of about 47 MPa. Noticeably, the development of the degradable glass-ceramics is helpful to the low-cost and pollution-free recycling of valuable metal electrodes, which is significant for the sustainable development of electronic packaging technologies.     

Experimental results for the vapor–liquid equilibria of (formaldehyde+1,3,5-trioxane+methanol+salt+water) systems and comparison with predictions

The salt effect on the vapor–liquid phase equilibrium (VLE) of solvent mixtures is of significant interest in the industrial production of 1,3,5-trioxane. Experimental data for the VLE of quinary systems (formaldehyde + 1,3,5-trioxane + methanol + salt + water) and their ternary subsystems (formaldehyde+salt+water), (1,3,5-trioxane+salt+water), and (methanol+salt+water) were system-atic measured under atmospheric pressure. The salts considered included KBr, NaNO3, and CaCl2. The extended UNIFAC model was used to describe the VLE of the salt-containing reactive mixtures. The model parameters were determined from the experimental VLE data of ternary systems or obtained from the literature, and then were used to predict the VLE of systems (1,3,5-trioxane + KBr + water), (methanol+KBr+water), (formaldehyde+KBr+water), and (formaldehyde+1,3,5-trioxane+methanol+salt+water) with salt=KBr, NaNO3, and CaCl2. The predicted results showed good agreements with the measured results. Furthermore, the model was used to uncover the salt effect on the VLE of these multi-solvent reactive systems.     

The refined e-NRTL model applied to CO2–H2O–alkanolamine systems

The electrolyte NRTL (e-NRTL) model by Chen (1982) and Chen and Evans (1986) is perhaps the most commonly used activity coefficient based thermodynamic model for industrial systems. It has been shown by Bollas et al. (2008) that the original e-NRTL model is inconsistent for systems with multiple cations and/or anions, in the same work the model equations for the so-called refined e-NRTL model were given. In this work the refined e-NRTL model is applied to CO₂–H₂O–alkanolamine systems. The interaction parameters of the refined e-NRTL model are regressed to partial pressure of CO₂, binary vapour–liquid-equilibrium, freezing point depression data and excess enthalpy data. The model is in the end used to predict partial pressures and speciation for the CO₂–H₂O–MEA and CO₂–H₂O–MDEA systems.     

Sintering properties and homogeneity of Ca2+-doped .65Y2O3–.35YCr0.5Mn0.5O3 NTC ceramics

Ceramics suitable for use over a wide temperature and having a negative temperature coefficient (NTC) based on .65Y₂O₃–.35YCr_0.5Mn_0.5O₃-doped with CaO were prepared by applying a solid-state reaction at different temperatures (1500–1650°C). The physical properties and scanning electron microscopy results revealed that dense NTC ceramics could be obtained by sintering at >1550°C. The effect of two different sintering methods on the properties of the NTC ceramics was studied, and the results indicated that the NTC ceramics obtained by employing the two-step sintering method exhibited better properties. The contents of Cr and Mn oxides in the NTC ceramic discs prepared by applying two-step sintering (1600°C) exhibited a decreasing trend from inside to outside. To quantify the diffusion rate, Fick's second law was used, and the diffusion coefficients of Cr and Mn oxides in the NTC ceramics were found to be 5.20 × 10^–5 and 2.36 × 10^–5 cm²/s, respectively. Resistivity and temperature analyses indicated that the resistivity (ρ₂₅), B_25/100, and B_700/1000 of the NTC ceramics were 1.61 × 10⁶ Ω cm, 2367 K, and 2697 K, respectively, which are suitable for a wide temperature range.     

Effect of Mg2+ and fluorine on the network and highly efficient photoluminescence of Eu3+ ion in MgF2–BaO–B2O3 glasses

The glass structure and photoluminescence of new oxyfluoride glasses with the composition of xMgF₂–(66.7−2x/3)BaO–(33.3−x/3)B₂O₃ (x = 10-50 mol%) were investigated in this work. The structure of the glasses was investigated by magic-angle spinning NMR, XAS, and Raman scattering spectroscopies. It was revealed that the glasses are mainly composed of BO₃ units with a disconnected borate network consisting mainly of ortho- and pyro-borate units, and ortho-borate increases with the addition of MgF₂. The fluorine atoms are surrounded by Mg²⁺ and Ba²⁺ ions. The photoluminescence of Eu³⁺-doped samples were investigated. It was indicated that asymmetry of the Eu³⁺ site increased with the addition of MgF₂. The photoluminescence quantum yield (η) of the glasses are very high and increased with MgF₂ addition; red photoluminescence is observed with η = 82% for 10MgF₂ and η = 98% for 50MgF₂ for excitation at 393 nm.     

Turbidimetric and intrinsic viscosity study of EVA copolymer–solvent systems

Both Hansen solubility parameter and Flory–Huggins interaction parameter of two EVA [Poly(ethylene-co-vinyl acetate)] copolymers with different vinyl acetate content have been obtained by means of intrinsic viscosity measurements. To calculate this last parameter it was also necessary to determine the theta solvent at different temperatures of the two EVA copolymers with turbidimetric measurements. The results indicate that the vinyl acetate content is a variable which influences the composition of the theta solvent and Flory–Huggins parameter (the higher the vinyl acetate content, the lower the Flory–Huggins parameter), although its influence over the Hansen solubility parameter is almost negligible.     

Imaging and chemical probing on the atomic scale: reconstruction and dynamics of the systems O2/Rh and NO2–H2/Pt

This paper presents two case studies of adsorbate-induced surface reconstruction, on the one hand, and dynamical reaction imaging along with local chemical probing, on the other hand. The first one deals with the oxygen-induced reshaping of 3D Rh crystals. Field ion microscopy (FIM) was applied to image in real-space the change from a nearly hemispherical shape in the absence of oxygen toward a polyhedral one in the presence of oxygen. Shape transformation occurs at temperatures of 380–550 K and is associated with the appearance of facets with {111} and {001} orientation. The only high-index planes present in the polyhedral form are of {137} symmetry. (1×2) and (1×3) missing-row reconstructions appear in the {113} and {011} planes. The polyhedral form has also been imaged under in situ conditions of the oxygen–hydrogen reaction on Rh at 505 K. The second case study deals with kinetic non-linearities occurring in the NO₂ reaction with hydrogen on the surface of a 3D Pt crystal reconstructed to a top- and edge-truncated pyramid. The reaction was found to ignite in the {012} corner planes of the crystal. One-dimensional wavefronts were subsequently observed to move along the 211 zone lines. These studies were performed by video-FIM and could be correlated with a local chemical analysis by time-of-flight mass spectrometry of ionised species. The mass spectrum provided information on water product (H₂O⁺ and H₃O⁺) and NO intermediate formation. Strong fluctuations in the NO ₂ ⁺ current indicated the occurrence of NO₂ surface diffusion. These species are most likely responsible for the field ion image formation.     

Effects of Water and Ion-Exchanged Counterion on the FTIR Spectra of ZSM-5. II. (Cu+–CO)-ZSM-5: Coordination of Cu+–CO Complex by H2O and Changes in Skeletal T–O–T Vibrations

The 2157 cm^–1 (strong) and 2108 cm^–1 (very weak) (CO) IR bands due to Cu⁺–CO in ZSM-5 zeolite with ¹²C and ¹³C isotopes, respectively, are reversibly red-shifted by subsequent adsorption of H₂O at 293 K. On the contrary, the locally perturbed internal (T–O–T) asymmetric stretching framework vibration [ _as ^int (TOT)(Cu⁺–CO)=965 cm^–1] is reversibly blue-shifted. The courses of the band shifts revealed notable features. Charge transfers from water to Cu⁺ ions, changes in coordination spheres of Cu⁺(CO)(H₂O) _n aqua complexes and secondary (solvent-like) effects were considered to explain the results.     

Preparation and characterization of Co2+ substituted Li–Dy ferrite ceramics

Stoichiometric compositions of ferrites with the chemical formula Li_0.5?0.5xCo_xFe_2.4?0.5xDy_0.1O₄ with x=0, 0.25, 0.5, 0.75, 1.0 were prepared by the standard double sintering ceramic method. X-ray diffraction analysis confirmed the cubic spinel structure of the prepared samples. The structural, morphological and magnetic properties were studied by X-ray diffraction, infra-red spectroscopy (IR), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM) and ac susceptibility measurements. Lattice constant, grain size and density increase whereas porosity decreases with the increase in Co²⁺ substitution. IR measurements show the characteristic ferrite bands. Spectral absorption bands were observed in IR spectroscopic analysis at ν₁=564?601 cm^?1, ν₂=486?519 cm^?1 and ν₃=551?578 cm^?1. The cation distribution estimated by the X-ray diffraction is supported by magnetization and susceptibility studies. The saturation magnetization decreases from 44.25 to 17.14 emu/g whereas coercivity remarkably increases from 240.69 to 812.14 emu/g with increasing Co²⁺ substitution. The mechanisms involved are discussed.     

Measurement and correlation of solid–liquid phase equilibria for binary and ternary systems consisting of N-vinylpyrrolidone, 2-pyrrolidone and water

The solid–liquid equilibria(SLE)for binary and ternary systems consisting of N-Vinylpyrrolidone(NVP),2-Pyrrolidone(2-P)and water are measured.The phase diagrams of NVP(1)+2-P(2),NVP(1)+water(2),NVP(1)+2-P(2)+1 wt%water(3)and NVP(1)+2-P(2)+2 wt%water(3)are identified as simple eutectic type with the eutectic points at 263.75 K(x_(1E)=0.5427),251.65 K(x_(1E)=0.3722),260.25 K(x_(1E)=0.5031)and256.55 K(x_(1E)=0.4684),respectively.The phase diagram of 2-P(1)+water(2)has two eutectic points(x_(1E)=0.1236,T_E=259.15 K and x_(1E)=0.7831,T_E=286.15 K)and one congruent melting point(x_(1C)=0.4997,T_C=303.55 K)because of the generation of a congruently melting addition compound:2-P·H_2O.The ideal solubility and the UNIFAC models were applied to predict the SLE,while the Wilson and NRTL models were employed in correlating the experimental data.The best correlation of the SLE data has been obtained by the Wilson model for the binary system of NVP+2-P.The UNIFAC model gives more satisfactory predictions than the ideal solubility model.     

Optical properties of novel oxyfluoride glasses on the systems of LaF3–LaO3/2–NbO5/2 and LaF3–LaO3/2–NbO5/2–AlO3/2

Oxyfluoride glasses of xLaF₃–(60 − x)LaO_3/2–40NbO_5/2 (x = 0, 5, 10, 35) and xLaF₃–(60 − x)LaO_3/2–30NbO_5/2–10AlO_3/2 (x = 0, 10, 20, 30) were prepared using a levitation technique. Both the glass-transition temperature, T_g, and onset crystallization temperature, T_c, were lowered by substituting a part of the oxygen with fluorine in the glasses. An appropriate amount of fluorine maximized the difference between the temperatures, ΔT (= T_c − T_g), indicating the improvement in the glass-forming ability. The atomic packing densities of the glasses were approximately 60%, which gradually increased with the fluorine content. The absorption edge of the glasses shifted toward the shorter wavelength region in the ultraviolet spectra and toward the longer region in the infrared spectra by fluorine substitution. In addition, in one of the oxyfluoride glasses, a wide transparency from 307 nm to 9.2 µm was realized. Furthermore, the glass exhibited superior optical properties, with a combination of a high refractive index, n_d, of 2.020 and low wavelength dispersion, v_d, of 30.1. The effect of fluorine substitution on the n_d and its v_d was analyzed using the Lorentz–Lorenz dispersion formula.     

Measurements and thermodynamic modeling of liquid–liquid equilibria in ternary system 2-methoxy-2-methylpropane+p-cresol+water

Liquid–liquid equilibrium(LLE)data for the ternary system 2-methoxy-2-methylpropane(methyl tert-butyl ether)+ p-cresol + water was measured at atmospheric pressure and temperatures of 298.15 K and 313.15 K.From the distribution coefficients and selectivity,it was found that 2-methoxy-2-methylpropane is an efficient solvent to extract p-cresol from wastewater.The consistency of the experimental tie-line data was verified with the Hand and Bachman equations.These data were also correlated with the non-random two liquid(NRTL)and universal quasi-chemical correlation activity coefficient(UNIQUAC)models to yield binary interaction parameters for p-cresol extraction process evaluation.Both models agreed with experiments very well,yet the NRTL model showed even smaller average deviation than the UNIQUAC model.